Weird one to break. All of them besides Metagross (which is unique for a number of reasons - only available in its original gen as a one off Gift, only gen with 2 Pseudos) have a base 45 catch rate until now. Frigibax follows that as expected, then Arctibax has 25, and finally Baxcalibur at 10. I guess Arctibax kinda makes sense? Them trying to make it more of a challenge than Frigibax and with Pokemon being easier to to find and spawn now. But Baxcalibur is only available in Tera Raids which have a 100% catch rate anyway… very weird all around.
Generally if a Pokemon line's catch rate isn't uniform across the line, it goes down with each stage even if the evolved forms aren't available to catch in the wild. I can't say what they were thinking with the Frigibax line but since Arctibax has a lower catch rate at 25, Baxcalibur naturally had to go even lower and the most appropriate catch rate to them was 10.
Giving Baxcalibur a catch rate in general was necessary as a failsafe in case someone hacks a Baxcalibur to be caught in the wild, for instance, as is the case with all Pokemon in any game.
Uniform catch rates were generally assigned to the other pseudos, the starter lines, fossils, and Eevee.
Dreepy in particular is just weird. The only pseudolegends with a highly restricted learnset are Dreepy and Beldum. Beldum evolves at lvl 20(the lowest of the pseudos), while Dreepy evolves at lvl 50, tied with Deino for the highest. And Beldum's moveset was Take Down only originally, which at least is interesting thematically/mechanically. Dreepy just...doesn't learn anything except via TM and all it's TM moves are awful.
Dreepy also is the only one with 270 BST. Frigibax is 320, and all others are 300. It's like they wanted it to be exceptionally weak(which sure, fine), but as someone who did a Pseudo-only run, they're all exceptionally weak in their initial forms. Unoptimized BST 300 and evolving at lvl 30 is already painful, making it evolve at lvl 50 just guarantees it's impossible to use Dreepy in-game at all. Which...why? Yeah, Dragapult is busted, it's a pseudo-legend, they're busted by design. It's no more busted than Garchomp or Salamence, so why did they make it miserable to train?
Evolutionary levels tend to be scaled to the point+level you encounter them in the wild in their debut game. Dreepy in wild encounters was found at Level 50-52 in SwSh in the Lake of Outrage, which made its high evolution level irrelevant back then as Dreepy would evolve immediately in one level anyway after being caught, or in 3 star raids which offer it in the high 30s, enabling 10-ish levels with a caught Dreepy before it evolved, based on the philosophy of "they want you to spend 10-15 levels with each stage before they evolve".
It's a case in general of non-dynamic evolution levels, which Gen 5's roster infamously suffers from with its later mons: it's sort of workable for their debut game, but not future compatible in the slightest when said mon is made available early, which Dreepy is evidently now suffering from in SV where it can be found much earlier than it was in SwSh. Dreepy does get it worse than most however because its low BST and non-existent movepool make it essentially "unusable until it evolves".
Pseudos in general tended to be scaled to what level they were found originally in their debut game. Beldum got it lucky because it was a Level 5 gift originally, and low evolution levels means it's very future compatible (aside from that stupidly bad catch rate) and can evolve quickly.
) and Alola arguably having three with one non-electric one (
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